The present invention relates to a thermal developing apparatus to thermally develop a photothermographic element and an assembling method thereof, and particularly, it is suitable when the present invention is applied to a medical image output apparatus.
A thermal developing apparatus which is heated while the photothermographic film is being interposed between a heated drum and a plurality of guiding rollers arranged around its periphery, and conveyed, in order to thermally develop the photothermographic film on which a latent image is formed by a laser exposure, is widely known. In such a thermal developing apparatus, the rollers are guided toward the heated drum, and the film is pressed onto the heated drum while the rollers are rotated at the time of thermally developing.
In this connection, the inventors discovered that in such a thermal developing apparatus, there is a case where the guiding roller is decentered due to the fluctuation at the time of production, and the photothermographic film is not uniformly pressed due to so-called the eccentricity of the guiding roller, and the adhesion of the photothermographic film becomes non-uniform, and the thermal energy which is obtained by the film from the heated drum is not uniform, and the uneven development is easily generated.
Further, at the time of the production of the apparatus or the assembling of the guiding roller in the cleaning or replacement in the maintenance, the degree of the uneven development is changed and fluctuated due to the condition of the arrangement of the rollers, and the reproducibility of the image quality is lost, and it is not preferable.
In view of the problems of the above-described conventional technology, the object of the present invention is to provide a thermal developing apparatus and an assembling method thereof in which the thermal energy which is obtained by the photothermographic element from the heated drum is uniformed, the fluctuation of the uneven development for each apparatus can be decreased, and the reproducibility and stability of the image quality at the time of the production and the maintenance of the apparatus can be secured.
In order to attain the above object, the first thermal developing apparatus according to the present invention is characterized in that: a thermal developing apparatus in which a photothermographic element having a latent image to obtain a visible image, includes a heated member positioned to receive the photothermographic element and to heat the photothermographic element for developing an image on the photothermographic element and a plurality of guiding rollers positioned at guiding positions adjacent the heated member for guiding the photothermographic element against the heated member, wherein the photothermographic element is transported between the heated member and the guiding rollers while the guiding rollers rotate, and the plurality of guiding rollers are arranged so that a variation cycle of the radius of each guiding roller is not synchronized with each other on the photothermographic element while the guiding rollers rotate. The variation cycle of the radius represents eccentricity of each roller (referred to JIS B0021-1974) which can be measured by, for example, a laser micro-measuring instrument or the like.
According to this thermal developing apparatus, even when the plurality of guiding rollers are respectively decentered, because the variation cycles are not synchronized, the radius variation is cancelled as a whole on the photothermographic element during the rotation of the plurality of guiding rollers, and the photothermographic element is more uniformly pressed onto the heated member as the whole by the plurality of guiding rollers. Therefore, the thermal energy obtained by the photothermographic element from the heated member becomes constant, and the uneven development is hardly generated.
Further, when a drive transmission means is provided between the heated member and the plurality of guiding rollers, because the guiding roller does not slip during the rotation, the arrangement of the plurality of guiding rollers which is made so that the variation cycle of the radius is not synchronized with each other, is not disordered.
Further, when a reference marker at which the phase of the variation cycle of the radius of each guiding roller is adjusted on the photothermographic element, is respectively provided on the plurality of guiding rollers, because the reference marker becomes an index when the reference marker positions each guiding roller at the time of the assembling, the reproducibility of the arrangement of the guiding roller is increased, and the reproducibility and the stability of the image quality can be secured at the time of the production and the maintenance of the apparatus. In this connection, the reference marker can be provided, for example, at the circumferential position at which the radius of the guiding roller is largest by the printing, or stamping.
Further, the second thermal developing apparatus according to the present invention is characterized in that: a thermal developing apparatus in which a photothermographic element having a latent image to obtain a visible image, includes a heated member positioned to receive the photothermographic element and to heat the photothermographic element for developing an image on the photothermographic element and a plurality of guiding rollers positioned at guiding positions adjacent the heated member for guiding the photothermographic element against the heated member, wherein the photothermographic element is transported between the heated member and the guiding rollers while the guiding rollers rotate, when the diameter of the guiding roller is defined as "PHgr", and the radius variation value of each guiding roller is defined as "sgr", the following expression is satisfied.
"sgr" less than "PHgr"xc3x970.1/12
According to this thermal developing apparatus, when the radius variation value "sgr" of a plurality of guiding rollers is within the range satisfying the above expression to the diameter "PHgr", because the photothermographic element is uniformly pressed onto the heated member by the plurality of guiding rollers, the thermal energy obtained by the photothermographic element from the heated member becomes constant, and the uneven development is hardly generated.
In this case, when the diameters of the plurality of guiding rollers are made respectively different, even when the plurality of guiding rollers are respectively decentered, because the variation cycles are not synchronized, the radius variation on the photothermographic element is cancelled as the whole during the rotation of the plurality of guiding rollers, and thereby, the photothermographic element is more uniformly pressed as a whole onto the heated member by the plurality of guiding rollers. In this connection, the plurality of guiding rollers whose diameters are different, may be arranged randomly and their assembling becomes easy.
Further, in an assembling method of the thermal developing apparatus according to the present invention, at the assembling at the time of the production or maintenance of the first thermal developing apparatus mentioned above in which the reference marker is provided on the plurality of guiding rollers, when the phase of the variation cycle of the radius of each guiding roller is adjusted and the plurality of rollers are arranged according to the reference marker, because the reference marker can be made an index for positioning at the time of the assembling of each guiding roller, the phase adjustment for each guiding roller becomes simple, and the assembling of the guiding roller becomes easy. Thereby, the reproducibility of the arrangement of the guiding roller is increased, and the reproducibility and stability of the image quality at the time of the production and the maintenance of the apparatus can be secured.
In this case, it is preferable that the diameter of each guiding roller is measured at the time of production of the thermal developing apparatus, and according to the measured value, the reference marker is provided.